Have you tried power cycling your router? Unplug the power cable for about 30 seconds, then reconnect it, wait for the connectivity lights to be stable and then reattempt connecting to a match. You can also set up a static ip address for your console to help create stability for your connection as well as prevent you from having to reconfigure your ports in the future. Also, you can follow the methods outlined here: Activision Support. If you choose to set up port forwarding, these port numbers may come in handy: